Between July and November 2002 researchers picked up acoustic signals of unprecedented clarity when recording seismic signals to measure earthquakes and tectonic movements on the Ekstroem ice shelf on Antarctica's South Atlantic coast.

They say the signal was similar to volcanic tremors from Kilauea and Mount St Helens.

Tracking the signal, the scientists found a 50 by 20 kilometre iceberg that had collided with an underwater peninsula and was slowly scraping around it.

"Once the iceberg stuck fast on the seabed it was like a rock in a river," says one of the study authors Dr Vera Schlindwein.

"The water pushes through its crevasses and tunnels at high pressure and the iceberg starts singing.